John was known as "John Junior". He showed an early interest in study. In 1771 he helped his father in surveying. In 1789 John Junior was disowned for "his meeting for business irregularities".

From the "History of Chester County, Pennsylvania", 1881:
"Several members of the family were surveyors, but the most ingenious in this line was John, the son of George, born in East Nottingham, PA on May 29, 1753.

"About the year 1778, he executed a map of the peninsula between the bays of Delaware and Chesapeake, including the State of Delaware and eastern shore of Maryland and Virginia.

"About the year 1790, he constructed a Variation Chart (or Magnetic Atlas), with a 'new plan', a book of explanation, and a Stereo Graphic Projection of the Spheres on a Plane of the First Magnetic Meridian. This 'new plan' met with violent opposition from some characters of eminence in the 'learned World' (as appears by publications yet extant), who could not relish that an obscure and self taught genius should acquire ideas that had so long escaped the penetration of men who had long been familiar with the illuminations of science.

"But whilst he was thus persecuted in the land of his nativity, he maintained an encouraging correspondence with Sir Joseph Banks, Esq.,Bart., President of the Royal Society of London, H. Parker, Secretary of the Commission of Longitude; also with the commissioners and secretaries of several learned societies and academies at Hamburg, Prussia, St Petersburg, Copenhagen, Lisbon, Cambridge, Paris, etc., and with George Washington, Thomas Jefferson and other liberal-minded men in America, who were pleased to say they highly approved of his laudable design of improving magnetic observations; that they acknowledged the originality and usefulness of his ideas and schemes; that the subject would derive no small increase from his ingenious works; that it was a work of great merit and might be of use in navigation; that they advised him to pursue with diligence a subject wherein his progress authorized a reasonable hope that science would derive a real increase, etc.

"In 1792 he embarked on a voyage to England and France, in order to pursue his researches, and with a view to apply his scheme to find longitude at sea." He returned about 1796.

"Having received invitation from a learned society in Russia, he visited Copenhagen, and thence to St Petersburg, where he met with great attention, was elected member of the Imperial Academy of Arts & Sciences, and received a golden medal with diplomatic honors thereof".

"He arrived in London the year of _____, still pursuing his studies with undeviating diligence. He received a silver medal from a society as an acknowledgement of some ingenious topographical discoveries.

"Sitting up late one night at his accustomed labors, he was found fallen in a paralytic affection, from which, after a few months, he so far recovered as to embark for home in the ship "William Murdoch", Capt Horn.

"He never arrived, but died at sea in the ship, 7/17/1805, aged about fifty years."